Method and device for regulation of the torque after a change in load for hybrid vehicles

ABSTRACT

The present invention is directed to a method for regulating the drive torque following a load change in hybrid vehicles, in which the drive torque is influenced in a load change in that a brake slip at the driven wheel of the hybrid vehicle as a result of the load change is already counteracted in the beginning phase, in such a way that any effect on the lateral stability and thus the stability of the hybrid vehicle during driving is excluded.  
     When brake slip occurs at the driven wheels ( 4, 5 ) because of a load change, it is provided that the drive torque is applied via the electromotor(s) ( 2 ) of the hybrid vehicle.

[0001] The present invention is directed to a method for regulating the drive torque following a load change in hybrid vehicles, in which the drive torque is influenced in a load change in that a brake slip occurring at the driven wheel of the hybrid vehicle in response to the load change is already counteracted in the beginning phase, in such a way that an effect on the cornering stability and thus on the stability of the hybrid vehicle during driving is obviated. Furthermore, the present invention is directed to a device for implementing the method of regulating the drive torque following a load change.

BACKGROUND INFORMATION

[0002] In motor vehicles it may happen that, because of the engine-drag torque, the driven wheels exhibit brake slip in response to a load change. This reduces the cornering stability of the motor vehicle and the motor vehicle becomes unstable. For this reason, it is necessary to reduce the brake slip as quickly as possible. It is generally known to use an engine-drag-torque control for this purpose in order to automatically regulate the engine torque in such a way that the brake torque disappears again as quickly as possible. Nevertheless, in conventional motor vehicles having a gasoline engine, a relatively long time elapses before the increase in the engine torque requested by the engine-drag-torque control has an effect on the driven wheels. The reason for this is that first the opening of the throttle valve and then the air-intake involve a time delay.

[0003] In order to prevent a decrease in the cornering stability of the vehicle, so that the vehicle stability remains unaffected, motor vehicles use traction control systems. Such systems, which prevent spinning of the driven wheels and regulate the traction slip to permissible values are known, for example, from “Kraftfahrtechnisches Taschenbuch” [Automotive Handbook], Robert Bosch GmbH, Düsseldorf, 21st edition, pages 555-559. The drive slip is regulated in that, for example, the drive torque is reduced when a limit value of the drive slip is reached. This reduction may be achieved by adjusting the ignition point or the internal combustion engine, or by other methods known per se. Regardless of the manner in which the known traction control systems reduce the drive torque once a limit value of the drive slip has been reached, the known traction control systems all have the inherent disadvantage that the traction control system is not only insufficiently controllable, but that the engine adjustment always involves a considerable time factor, so that, overall, a certain time characteristic of the drive torque reduction cannot be achieved.

[0004] From DE 195 49 259 A1, a traction control system for hybrid vehicles is also already known that avoids the disadvantages inherent in the traction control systems used in conventional motor vehicles. This is achieved by a drive system having a traction control system in which the electromotor is configured in such a way that it reduces the drive slip by lowering the drive torque of the drive unit, this being accomplished by the action of the brake and/or by clutch slip action in electromotors acting as clutch. In this case, the traction control system takes action only when a limiting value of the drive slip is exceeded. If a condition resulting therefrom is then present, this traction control system reduces the drive torque acting on the driven wheels with the aid of the electromotor.

SUMMARY OF THE INVENTION

[0005] The present invention provides a method and a device for regulating the drive slip following a load change in hybrid vehicles in that both the method and the device increase the drive torque as quickly as possible when the driven wheels exhibit brake slip in response to a load change. In this way, the lateral stability of the hybrid vehicle is also maintained in a load change and the hybrid vehicle thus retains its stability during driving.

[0006] These advantages are achieved by a method in which the drive torque is applied via the electromotor(s) of the hybrid vehicle when a brake slip occurs at the driven wheels in response to a change in load. In implementing the method once a brake slip has been detected following a load change, the setpoint drive torque is calculated and input for a drive control in which the setpoint torque for the internal combustion engine and the setpoint torque for the electromotor(s) are determined by an algorithm for the operating strategy and the setpoint torque of the electromotor(s) is set to be equivalent to the setpoint drive torque if the setpoint drive torque is less than or equal to the maximum possible drive torque of the electromotor(s) in the instantaneous operating point. A precondition for adjusting the setpoint torque of the electromotor(s) so that it is equivalent to the setpoint drive torque is always that a query regarding the charge state of the battery has indicated that the battery holds a sufficient charge.

[0007] If the condition according to which the setpoint drive torque be less than or equal to the maximally possible drive torque of the electromotor(s) in the instantaneous operating point is not satisfied, the combustion engine, in a further development of the method according to the present invention, applies the portion of the torque that exceeds the maximally possible drive torque of the electromotor(s). In order to achieve this, that it, in order to apply the share of the drive torque that exceeds the maximally possible drive torque of the electromotor(s) by way of the internal combustion engine, the electromotor(s) is/are controlled in such a way that the setpoint torque associated with them is equivalent to the maximally possible drive torque of the electromotor(s) in the instantaneous operating point. The internal combustion engine is controlled in such a way that the setpoint torque associated with it is equivalent to the setpoint drive torque minus the maximally possible drive torque of the electromotor(s) in the instantaneous operating point. In this way, it is achieved that the electromotor(s), which generate(s) drive torque considerably faster than an internal combustion engine, is/are able to apply the highest possible portion of the required drive torque as quickly as possible.

[0008] On the assumption that the response time of the electromotor(s) is very brief if it/they is/are energized already, the electromotor(s), in implementing the method according to the present invention, is/are already fully energized at the beginning of the load change in that its/their lead value is set to a value that is equivalent to the maximally possible drive torque of the electromotor(s) in the instantaneous operating point. If the engine drag-torque control then specifies an increase in the drive torque, it will not be necessary to first generate the excitation of the electromotor(s). It must be considered here that a load change is detected, for example, by the accelerator value decreasing rapidly or by a gear-shift procedure being initiated.

[0009] The detection of brake slip following a load change, on the basis of which the setpoint drive torque is calculated and input for the drive control, is implemented on the basis of data resulting from the signals that are associated with the speeds of the driven wheels.

[0010] The effects intended by the present invention are not only attained when the method according to the present invention is applied in hybrid vehicles having two-wheel drive, but also when it is applied in hybrid vehicles having all-wheel drive.

[0011] To implement the method according to the present invention, a device is provided in which each driven wheel is assigned a wheel-speed sensor that detects the speed of the driven wheels. The wheel-speed sensors are in operative connection with a wheel control in such a way that it is able to detect brake slip following a load change if the wheel control receives information regarding a brake slip via signals generated by the wheel-speed sensors. The wheel control is able to calculate the setpoint-drive torque of the hybrid vehicle, which it inputs for a drive control where both the setpoint torque for the internal combustion engine and the setpoint torque for the electromotor(s) are ascertainable by an algorithm for the operating strategy.

[0012] In this device, after querying the charge state of the battery and ascertaining a sufficient load state, the drive control is able to set the setpoint torque of the electromotor(s) to be equivalent to the setpoint drive torque, if

M_(MSR) ^(x)≦M_(EM) _(—) _(Max),

[0013] M_(EM) _(—) _(Max) representing the maximally possible drive torque of the electromotor(s) in the instantaneous operating point.

[0014] If the condition

M_(MSR) ^(x)≦M_(EM) _(—) _(Max)

[0015] is not satisfied, the drive control of the system is able to control the electromotor(s) in such a way that its/their setpoint torque is equal to the maximally possible drive torque in the instantaneous operating point and the internal combustion engine is able to be controlled in such a way that its setpoint torque is

M _(VM) ^(x) =M _(MSR) ^(x) −M _(EM) _(—) _(Max)

[0016] The device ensures that the electromotor(s) is/are fully energizable at the beginning of a load change in that its/their lead value

M_(EMVor) ^(x)−M_(EM) _(—) _(Max)

[0017] is able to be set, so that the response time of the electromotor(s) is very brief.

BRIEF DESCRIPTION OF THE DRAWING

[0018] The present invention is explained in the following in an exemplary embodiment with the aid of the pertinent drawing, which illustrates a block diagram of a device for realizing the method of regulating the drive torque following a load change in hybrid vehicles.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0019] In the block diagram shown in the drawing, a hybrid vehicle having 2-wheel drive is assumed, in which an electromotor 2 is provided in addition to internal combustion engine 1. Via a transmission, internal combustion engine 1 as well as electromotor 2 are in operative connection with driven wheels 4, 5 of the hybrid vehicle. An engine control 6 is assigned to internal combustion engine 1, and a converter 7 to electromotor 2. Internal combustion engine 1 introduces a torque M_(VM) (signal 18) and electromotor 2 introduces a torque M_(EM) (signal 19) into the drive train.

[0020] In order to be able to increase the drive torque in these hybrid vehicles as quickly as possible when driven wheels 4, 5 exhibit brake slip in response to a load change, that is, in order to retain the lateral stability in a load change of the hybrid vehicle so that the hybrid vehicle retains its stability during driving even when brake slip occurs at driven wheels 4, 5 due to a load change, the drive torque is applied via electromotor 2.

[0021] According to the drawing, essential components of the device for regulating the drive torque following a load change in the hybrid vehicle are wheel speed sensors 8, 9, which are assigned to driven wheels 4, 5 and detect the speed of driven wheels 4, 5; a wheel control—ESP, ABS—10, and a drive control 11. Wheel speed sensors 8, 9 are in operative connection to wheel control 10, in such a way that it detects brake slip following a load change when wheel control 10 receives signals 12 n_(wheel-left) and 13 n_(wheel-right), generated by wheel speed sensors 8, 9, with information regarding a brake slip. If wheel control 10 has detected brake slip following a load change, wheel control 10 inputs the setpoint drive torque M_(MsR) ^(x) (signal 14) of the hybrid vehicle for drive control 11, where both the setpoint torque M_(VM) ^(x) (signal 15) for internal combustion engine 1 and also setpoint torque M_(EM) ^(x) (signal 16) for electromotor (signal 16) are ascertained via an algorithm for the operating strategy.

[0022] At the same time, drive control 11 queries the charge state of the battery, which is not shown further in the block diagram. If the query has shown that the battery is sufficiently charged, drive control 11 sets setpoint torque M_(EM) ^(x) of electromotor 2 so that it is equivalent to setpoint drive torque M_(MSR) ^(x) if drive torque M_(MSR) ^(x) is less or equal to the maximally possible drive torque M_(EM-Max) of electromotor 2 in the instantaneous operating point. If drive control 11 determines that the condition

M_(MSR) ^(x)≦M_(EM-Max)

[0023] is not satisfied, drive control 11 controls electromotor 2 in such a way that its setpoint torque M_(EM) ^(x) is equivalent to the maximally possible drive torque M_(EM-Max) in the instantaneous operating point. If the condition

M_(MSR) ^(x)≦M_(EM-Max)

[0024] is not satisfied, internal combustion engine 1 is controlled in such a way that setpoint torque M_(VM) ^(x) assigned to internal combustion engine 1 is equivalent to to setpoint drive torque M_(MSR) ^(x) minus the maximally possible drive torque M_(EM-Max) of electromotor 2 in the instantaneous operating point. In this way, it is achieved that internal combustion engine 1 applies the portion of the drive torque that exceeds the maximally possible drive torque M_(EM-Max) of electromotor 2 in the instantaneous operating point, so that electromotor 2 applies the highest possible portion of the required drive torque as quickly as possible.

[0025] Although not shown further in the drawing, electromotor 2 should always be fully energized at the beginning of a load change in that the lead value M_(EMVor) (signal 17) of setpoint torque M_(EM) ^(x) of electromotor 2 is set to be equivalent to the maximally possible drive torque M_(EM-Max) in the instantaneous operating point. If the generally known engine-drag torque control (likewise not shown further) then specifies an increase in the drive torque, it will not be necessary to first generate the excitation of electromotor 2. Thus, electromotor 2 is already energized and its response time is very rapid should it be required to apply the drive torque when brake slip occurs at driven wheels 4, 5 in response to a load change. 

What is claimed is:
 1. A method for regulating the drive torque following a load change in hybrid vehicles, in which the drive torque is influenced in a load change in that a brake slip at the driven wheels of the hybrid vehicle resulting from a load change is already counteracted in the beginning phase, in such a way that an effect on the lateral stability, and thus on the stability of the hybrid vehicle during driving, is excluded, wherein, when brake slip occurs at the driven wheels (4, 5) because of a load change, the drive torque is applied via the electromotor(s) (2) of the hybrid vehicle.
 2. The method as recited in claim 1, wherein, upon detection of a brake slip following a load change, the setpoint drive torque (M_(MSR) ^(x)) is calculated and input for a drive control (11) in which the drive torque (M_(VM) ^(x)) for the internal combustion engine (1) and the drive torque (M_(EM) ^(x)) for the electromotor(s) are determined by an algorithms for the operating strategy, and which sets the setpoint torque (M_(EM) ^(x)) of the electromotor(s) to be equivalent to the setpoint drive torque (M_(MSR) ^(x)) if the setpoint drive torque (M_(MSR) ^(x)) is less or equal to the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) (2) in the instantaneous operating point.
 3. The method as recited in claim 2, wherein the setpoint torque (M_(EM) ^(x)) of the electromotor(s) (2) is set to be equivalent to the setpoint drive torque (M_(MSR) ^(x)) if a query of the charge state of the battery has shown that it is sufficiently charged.
 4. The method as recited in claim 3, wherein, if the condition according to which the setpoint drive torque (M_(MSR) ^(x)) be less or equal to the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) (2) in the instantaneous operating point, is not satisfied, the internal combustion engine (1) applies the portion of the drive torque that exceeds the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) (2).
 5. The method as recited in claim 4, wherein, for the internal combustion engine (1) to apply the portion of the drive torque that exceeds the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) 2, the electromotor(s) is/are controlled in such a way that the setpoint torque (M_(EM) ^(x)) assigned thereto is equivalent to the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) (2) in the instantaneous operating point, whereas the internal combustion engine (1) is controlled in such a way that its assigned setpoint torque (M_(VM) ^(x)) is equivalent to the setpoint drive torque (M_(MSR) ^(x)) minus the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) (2) in the instantaneous operating point.
 6. The method as recited in claim 5, wherein at the beginning of the load change, the electromotor(s) (2) is/are fully energized in that their lead value (M_(EMVor) ^(x)) is set to be equivalent to the maximally possible drive torque (M_(EM-Max)) of the electromotor(s) (2) in the instantaneous operating point.
 7. The method as recited in claim 2, wherein the detection of brake slip is implemented on the basis of data resulting from the signals (n_(wheel-left)) and (n_(wheel-right)) assigned to the speeds of the driven wheels (4, 5).
 8. The method as recited in one or more of the preceding claims 1 through 7, wherein the method for applying the drive torque in a load change is implemented both in hybrid vehicles having 2-wheel drive and also in hybrid vehicles having all-wheel drive.
 9. A device for carrying out the method as recited in claims 1 through 8, wherein each driven wheel (4, 5) is assigned a wheel speed sensor (8, 9) detecting the speed of the driven wheels (4, 5), the wheel speed sensors (8, 9) being in operative connection with a wheel control (10) in such a way that they are able to detect brake slip following a load change when the wheel control (10), via signals (n_(wheel-left)) and (n_(wheel-right)) generated by the wheel speed sensors (8, 9) receives information about a brake slip, the wheel control (10) being able to calculate the setpoint drive torque (M_(MSR) ^(x)) of the hybrid vehicle, which it inputs for a drive control (11) in which both the setpoint torque (M_(VM) ^(x)) for the internal combustion engine (1) and the setpoint torque (M_(EM) ^(x)) for the electromotor(s) (2) are able to be determined by an algorithm for the operating strategy.
 10. The device as recited in claim 9, wherein, upon querying the charge state of the battery and ascertaining a sufficient charge state, the drive control (11) is able to set the setpoint torque (M_(EM) ^(x)) of the electromotor(s) (2) to be equivalent to the setpoint drive torque (M_(MSR) ^(x)) if M_(MSR) ^(x)≦M_(EM) _(—) _(Max,) M_(EM) _(—) _(Max) representing the maximally possible drive torque of the electromotor(s) (2) in the instantaneous operating point.
 11. The device as recited in claim 10, wherein the electromotor(s) (2) is/are controllable by the drive control (11) in such a way that its/their setpoint torque (M_(EM) ^(x)) is equivalent to the maximally possible drive torque (M_(EM) _(—) _(Max)) in the instantaneous operating point, and the internal combustion engine (1) is able to be controlled in such a way that its setpoint torque is M _(VM) ^(x) =M _(MSR) ^(x) −M _(EM) _(—Max) if the condition M_(MSR) ^(x)≦M_(EM) _(—) _(Max) is not satisfied.
 12. The device as recited in claims 10 and 11, wherein the electromotor(s) (2) is/are fully energizable at the beginning of a load change in that its/their lead value M_(EMVor) ^(x)=M_(EM) _(—) _(Max) is able to be set. 